Control of heat transfer in circular channels using oblique triangular ribs

Abstract

Enhancing heat transfer is crucial for improving the performance of heat transfer applications. Therefore, a novel method is proposed in this study for improving the heat transfer using a new rib geometry within a circular channel. The performance of the novel method was evaluated by comparing the results of the channel with ribs with that of an ordinary channel. In this study, numerical investigations were conducted on the temperature distribution and fluid flow properties of a 500 mm tube with an external diameter of 50 mm and an internal surface of 47 mm. To evaluate the effects of the ribs on the heat transfer via the tube wall, the tube was maintained at a steady temperature of 673 K, and the Reynolds number (Re) was set in the range of 1000–20000. Different cases were simulated using CFD-FLUENT (v. 16.1). For the three cases, three types of ribs (7 in total) with triangular transverse sections of 5 mm were set 62.5 mm apart in the tube. Subsequently, the turbulent parameters (k, ε) affecting the turbulent flow were evaluated. Moreover, the heat transfer coefficient and friction coefficient of the tube with ribs were calculated using the enhancement technique and compared with those of the plain tube. It was observed that the ribs inside the tube increased the temperature of the cooling air in the first, second, and third cases by 6.25%, 12.5%, and 17.5%, respectively. Furthermore, the difference in the velocity and temperature distribution across the centreline of the tube was observed for all three cases and a smooth tube. It was observed that the heat flow rate increased, particularly around Re = 14,000, in the ribbed tube. The tube with ribs exhibited a 90% increase in the flow rate compared to the flow rate in the tube with no ribs. The tube with ribs also exhibited better performance in terms of turbulent flow.